This section provides background information related to the present disclosure which is not necessarily prior art.
Profile rails are known in many embodiments; DE 20 2012 002 005 U1 shows one example. Known profile rails, as perforated profile rails, are provided with a row of holes to clip in cage nuts. Cage nuts are mostly square nuts that are held in a similarly square cage of sheet metal. By means of the cage, the nut can be fixed to a sheet of metal, so that a thread can be provided even on thin sheets, such as profile rails, in which a thread cannot be cut. Cage nuts are standardized in DIN 557.
Normally, profile rails are attached to the side walls of racks, so that 19-inch industrial standardized appliances can be bolted to the front panel through attaching holes provided in the appliance on the left and right in said panel and held securely. Usually, the appliances are attached using four bolts in the corner areas of their front plate, sometimes also using two bolts at both ends of the center line of the front plates. The height of the front plates of the industrial standardized appliances is determined by a grid in units of height, where one unit of height is specified as 1.75 inches, or 44.45 mm.
A 19-inch rack system also follows certain standards, or is standardized, for example by IEC 60297 or the corresponding metric grid system following IEC 60917. Profile rails can also be used outside of racks, right down to the individual rail that is installed horizontally or vertically.
If cage nuts are to be used when attaching appliances in 19-inch rack systems, the matching profile rail has a square hole that is somewhat smaller than the cage so that a support is available between sheet metal nut to absorb axial thread forces. The cage nuts must be pre-tightened manually in order to position them in the square cutouts in the profile rails, where there is a risk of their twisting and slipping. Removing a cage nut is correspondingly laborious and often requires considerable effort. In the case of a cage nut, quick fastening is out of the question.